The invention relates to a magnetic head for a magnetic recording and playback apparatus, which head comprises a Mn--Zn-ferrite core having two core parts between which a transducing gap is formed.
It is known tht the use of ferrites, in particular monocrystalline Mn--Zn-ferrites, as magnetic core materials of magnetic heads is desired for use in apparatus for magnetic tape recording and playback, for example, in audio and video tape recorders. This desirability is because ferrites are available which have the advantage of high resistance to detrition and very good magnetic properties, for example, with respect to magnetic saturation, coercive force and permeability, and good frequency characteristics.
The strength of the magnetic fields which are generated at the area of the transducing gap by a magnetic head to write information on a magnetic medium depend directly on the saturation magnetization of the material of the core of the magnetic head. Magnetic heads for present-day video recorders usually have a core of a Mn--Zn-ferrite. This type of material has a saturation magnetization 4.pi.M.sub.s of approximately 500 mT (5000 Gauss) at room temperature. The magnetization of these MnZn ferrites at temperatures which are slightly above room temperature satisfies the requirements which are imposed upon writing of information on conventional tapes, such as CrO.sub.2 tape having a coercive force H.sub.c of approximately 56 kA.sup.2 /m (700 Oersted).
However, in order to improve the quality of the video recording process, there is the tendency to replace the conventional magnetic tapes by magnetic tapes having a high coercive force, such as tapes on the basis of pure Fe which have a H.sub.c of approximately 88-136 kA/m (1100-1700 Oersted). The use of such magnetic tapes requires the materials of the magnetic core to have a larger value of the saturation magnetization (4.pi.M.sub.s) than the presentday ferrite materials. Such as material does exist but it has other properties which differ from the properties of these ferrite materials which make it less suitable for the applications in view. This material, Sendust, an alloy of approximately 85% by weight Fe, 10% by weight Si and 5% by weight Al, has a saturation magnetization 4.pi.M.sub.s which is considerably higher than 500 mT. However, it has a resistivity of 10.sup.-6 .OMEGA. m which is three orders of magnitude smaller than the resistivity of monocrystalline Mn--Zn-ferrites. Because of this low resistivity, the core of a video Sendust head must be constructed from a number of electrically insulated laminations. Moreover, Sendust is less resistant to detrition than ferrites.